1. Field of the Invention
The invention relates to a method and apparatus for enriching an engine. More particularly, the invention relates to automatically and variably enriching an all terrain vehicle engine with fuel and/or air as appropriate for different engine temperatures.
2. Description of Related Art
Vehicles, such as all terrain vehicles, conventionally include an engine such as an internal combustion engine in order to enable them to move under their own power. It is sometimes useful to provide additional fuel and/or air to an engine when it is running below its normal operating temperature. This may be true particularly, though not exclusively, when the engine is being started. The process of adding additional fuel and/or air is referred to herein as “enrichment”, and a device for providing enrichment is referred to herein as an “enrichener”.
As the term is used herein, an “all terrain vehicle” or “ATV” is defined as a motorized vehicle suitable for travel on surfaces other than paved roads or highways (though not necessarily unsuitable for travel on highways or paved roads). ATVs travel on low-pressure tires, typically four in number, and generally have a seat designed to be straddled by an operator. The seat may be designed to support one or more additional passengers in addition to the operator, and/or there may be one or more additional seats. Typically, passengers are seated in-line behind the operator. ATVs generally use handlebars for steering control.
Unless otherwise indicated, the term “vehicle” when used herein refers specifically to an all terrain vehicle.
Instances wherein enrichment may be desirable include, for example, occasions when the vehicle's engine is started while cold. Typically, the normal operating temperature of such engines is significantly higher than the ambient temperature. When the engine is below this temperature, it may be helpful to provide the engine with additional fuel and air until such time as the engine temperature approaches its normal operating range. Once the engine reaches its operating temperature, enriching can be discontinued. Engine enrichment may be advantageous in other circumstances, as well.
It is known to manually enrich a vehicle engine. For example, a manual enrichener may be provided with a hand control, which when activated by the vehicle's operator sends additional fuel and air to the engine.
However, the manual nature of such an arrangement has several drawbacks. For example, the vehicle operator must activate the enrichener each time it is needed. If the operator does not activate a manual enrichener, no extra fuel or air will be provided. In addition, if the operator fails to deactivate a manual enrichener, or activates it when it is not needed, the engine may be supplied with unnecessarily large amounts of fuel and/or air. This may be wasteful of fuel, may make the vehicle's engine run differently than intended, etc.
A conventional manual enrichener does not in itself provide feedback to the operator as to when it should be activated. Thus, unless some feedback mechanism is provided for the operator, there may be no convenient way for the operator to tell whether enrichment is appropriate. For example, although as noted enrichment may be desirable when starting a cold engine, it may not be desirable when starting an engine that is already warm, i.e. one that was used recently and has not fully cooled down. Even assuming the vehicle operator has kept careful track of the time since the vehicle was last operated, the rate of engine cooling can depend on many factors, such as ambient temperature, wind, etc., so in many circumstances it may not be readily apparent whether the engine has cooled enough that enrichment is appropriate.
In addition, at times it may be desirable to activate the enrichener at less than full output, that is, to add fuel and air, but not at the maximum rate possible for the enrichener. For example, if the engine is started at a temperature below its operating range, but above ambient temperature, it may be preferable to enrich the engine only slightly. Similarly, it may be desirable to vary the level of engine enrichment over time, i.e. reducing it as the engine warms.
However, for a manual enrichener, any judgment of whether to enrich the engine and to what degree must be made consciously by the operator, and likewise any adjustments to the enrichment require the operator's attention.
Attempts have been made to produce an automatic enrichener. It is possible to produce an electronic enrichener that includes an engine temperature sensor, a control processor, an adjustable enrichment valve, and an actuator for adjusting the enrichment. However, such conventional devices typically are complex and expensive to manufacture and install, and have not proven entirely satisfactory.